1. Field of the Invention
The present invention relates to an adhesive film which is used for connecting an electrical part to a substrate, a connecting method thereof, and a joined structure.
2. Description of the Related Art
An anisotropic conductive adhesive has been conventionally used for connecting an electronic part or a wiring board to a substrate. The anisotropic conductive adhesive contains a binder and conductive particles dispersed in the binder.
When the anisotropic conductive adhesive is placed between the surface of the substrate where the terminals are disposed and the surface of the electronic part where the terminals are disposed, and heated and pressurized, the softened binder is pushed out from the space between the terminal of the substrate and the terminal of the electronic part, and the conductive particles are held between the terminal of the substrate and the terminal of the electronic part, to thereby electrically connect the substrate and the electronic part.
However, when the binder is pushed out, a part of the conductive particles is pushed out together with the binder, and the pushed conductive particles are moved into the space between the adjacent terminals of the substrate or the adjacent terminals of the electronic part, which may cause a short circuit due to the conductive particles present between the adjacent terminals.
Moreover, when the conductive particles are pushed out from the space between the terminal of the substrate and the terminal of the electronic part, the number of the conductive particles which can be held between the terminal of the substrate and the terminal of the electronic part is decreased, lowering the conduction reliability (see Japanese Patent Application Laid-Open (JP-A) Nos. 2006-32335 and 07-230840).